Rheostat



Dec. 14 1926.

A. BOEDEKER ET AL RHEOSTAT Filed March '7, 1925 FIG. 2.

Patented Dec. 14, 1926.

UNITED STATES PATENT ()FFICE.

ANTHONY BOEDEKEB, OF CINCINNATI, AND JESSE S. "NENTWORTH, ()F NGIt-VIOOD. OHIO, ASSIGNORS TO GRANDTONE EADIO CORPGREJILAQN. F CINCTNNATI, OHIO, .A

CORYOBA'IION OF OHIO.

RHEOS'I'AT.

Application filed March 7, 1925.

Our rheostat is particularly designed for use in radio sets, for controlling the potential of electric current used in radio vacuum tuhes.

One of the features of our invention consists in the employment of a shaft suitably mounted and having a screw threaded end, in combination with a cylindrical drum mounted on said shaft, and a resisting wire coil spirally wound upon said drum, each coil turn spaced from its adjacent coil turn, the pitch of the spiral coil being the same as the pitch on the screw end of the shaft so that the turning of said shaft through the medium of a turn dial at its one end will result in a dependable rotatable n'iovement of the shaft and the drum and resistance coil, so that the turns of the coil will uniformly engage a contact blade or point which is spring controlled, thus producing an adjustable .slidable continuous metallic contact.

Another feature consists in providing means for taking up any elongation of the resisting wire.

Another feature consists in providing a contact point or blade having a grooved end for engaging with the resistance coil.

Other features and advantages will readily become apparent from reading the following specification.

In the accompanying drawing, forming part of this specification:

Fig. 1, is a front elevation of a rheostat embodying our invention,

Fig. 2, is a section on line 22 of Fig, 1,

Fig. 3, is a plan view, in elevation, and

Fig. t, is an enlarged detail, showing the contact blade engaging the resistance coil.

The frame work of the rheostat in the present instance is composed of sides 1, bottom 2, and top 8.

Through the sides 1, We place and support a spindle or shaft 4, upon which is mounted a drum 5, carrying the resistance wire coil 6, so arranged that spaces 7 are present be tween each coil turn of the wire, forming the said resistance coil.

A contact blade 8, having a grooved contact end 9 is held against or in contact with Serial No 13,768.

said wire coil (3, by reason of the spring l0 pressing downwardly on the blade 8, said blade being loosely or slidably mounted in the top 3 of the framework. A screw 12, holds the spring 10 in position and is also used as one terminal for a wire 13; the other terminal it for the wire 15, supports the contact plate 16, against one side 1, of the frame; this contact plate allows the current to pass from the wire 15 to the shaft or spindle 4t, having screw threaded end 17 allows the drum 5, with its wire coil (3 to move backwardly and forwardl in other wor s, to decrease or increase tl 1e amount of re sistance, as the dial 18 is revolved.

A wire 19, having one end soldered or fastened to the shaft or spindle t its other end soldered or fastened to the first coil turn 20, or coil (3, completes the circuit between the two wires 13 and 15.

A tension spring 21, is provided as a take up for the expansion and contraction of the resistance coil 6? the spring has one end fastened at point 22 to the last coil turn or lap of the resistance coil 6 and the other end fastened to the drum at the point 2%.

It may be stated that the screwed end 17 of the spindle 4, is of the same pitch as the coil 6, in order to produce positive dependable adjustment.

We do notlimit ourselves to the precise form and construction herein set forth, but may alter and modify the same to some extent, so long as said alterations and modifications fall within this specification and claims, however, the device herein described being a preferred form.

lVhat we claim as new and our invention and desire to secure by Letters Patent is:

1. In a rheostat, a frame, a shaft mounted for longitudinal and rotary movement within said frame, a drum carried by said shaft, a coil on said drum, a contact blade slidably arranged in said frame and having its inner end grooved and in contact with said coil, and a spring secured at one end to said frame, and bearing at its opposite end upon the outer extremity of said blade to yieldably hold the inner end of the latter in en gagement with said coil.

blade and normall holding the inner end 3 a thereof in en 'a einent with said end. 10

b b In testimony whereof, We affix our signatures at clncinnatl, Ohio, rhls lth day of March, 1925.

ANTHONY BOEDEKER. JESSE S. WENTYVORTH. 

